Piezoresistive Response of Spray-coated Multiwalled Carbon Nanotube/Glass Fiber/Epoxy Composites under Flexural Loading

The piezoresistive response of multiscale composite laminates under monotonic and cyclic flexural loading was experimentally investigated herein. For that purpose, unidirectional glass fibers were coated with multiwalled carbon nanotubes (MWCNTs) by spray coating technique in order to create electrically percolated networks into composites. Then three-point bending tests and electrical resistance measurements were simultaneously conducted on both tensile and compressive sides of the beam-type specimens. The results of the electromechanical tests indicated that the multiscale composite laminates show good piezoresistive sensing characteristics with excellent cyclic stability and reproducibility suitable for in-situ damage detection and strain monitoring through their electrical resistance change. Determination of the gauge factors of specimens with different MWCNTs contents exhibited a significant sensitivity enhancement for composites comprising MWCNTs content higher than 0.5 wt.%. Fractured specimen examination by scanning electron microscopy revealed failure modes mainly located near the top surface of the specimens, being in good agreement with piezoresistive measurements.